Naoki Tohyama, PhD

Spine stereotactic body radiotherapy (SBRT) requires high precision due to the anatomical proximity of target to the spinal cord and steep dose gradients. Rotational setup errors (SE) can affect the dose delivery to targets and organs at risk (OAR). This stud...

Computed tomography-derived pulmonary perfusion (CTQ) imaging is an emerging, accessible modality that derives regional pulmonary perfusion information from CT datasets. To facilitate clinical translation of this new technology, we compared two CTQ metrics: n...

Stereotactic body radiotherapy (SBRT) for spinal metastases requires accurate delineation of the spinal cord and thecal sac to maximize treatment efficacy while minimizing toxicity. Deep learning-based segmentation models improve contouring efficiency and red...

Deep learning-based organ contouring is essential for optimizing the MR-guided adaptive radiotherapy (MRgART) workflow. However, online contouring remains challenging because of interfractional anatomical variations. This study demonstrated the effectiveness...

The novel Varian TrueBeam HyperSight-CBCT (HS-CBCT) aims to overcome image non-uniformity and artifacts in conventional CBCT. While radiomic feature repeatability has been investigated for conventional CBCT, the performance of HS-CBCT remains under-evaluated....

This study aimed to quantitatively investigate the robustness of virtual bolus (VB)–generated skin flash under respiratory motion in breast volumetric modulated arc therapy (VMAT) using measurement-based dosimetry.

Jaw geometry in elongated fields substantially impacts output factors (OPFs); therefore, reliance on square-field data alone cannot account for the physical effects. This study evaluated the response characteristics of various small-volume detectors in high-a...

Deep-inspiration breath-hold radiotherapy (DIBH) is widely used in left-sided breast cancer radiotherapy to reduce heart dose, but the dosimetric benefit varies among patients. Assessing DIBH eligibility typically requires additional CT simulation and treatme...

Stereotactic body radiotherapy (SBRT) for non-spinal bone metastases generally achieves high local control; however, approximately 10% of patients experience local failure (LF). Conventional clinical and dose metrics often fail to capture patterns associated...

Accurate detector alignment is essential in MR-linac reference dosimetry to account for Lorentz force–induced dose perturbations. Current protocols, such as AAPM TG-351, recommend aligning the detector’s longitudinal axis parallel to the magnetic field (B0) t...

Grade ≥2 radiation pneumonitis (RP) occurs in approximately 30% of patients undergoing radiotherapy for lung cancer. Therefore, a predictive model to estimate RP risk before radiotherapy is required. Radiomics and dosiomics have shown potential for RP predict...